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DCPR Power RangesProposed for CS v.2.0

DCS Manufacturers Meeting June 13, 2007Peter Woolner

Noblispwoolner@noblis.org

703-610-1724

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Power Levels for CS v.2.0

• The 2 dB ranges proposed at Asheville are not practical: a range of at least 4 dB will be necessary

• The satellite transponder functions best with the minimum possible EIRP range

• Wider range of EIRP must also result in higher minimum EIRP

• Higher EIRPs consume extra input power at the DCP location

• Assumes no CDMA during the transition

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• Proposed EIRP ranges for system design:– 300 bps: 37 dBmi to 41 dBmi– 1200 bps: 43 dBmi to 47 dBmi

• Assumes reception at DRGS with 15 dB/K G/T and “worst case” transponder loading

• Other relevant factors:– Based on actual measured GOES-13 performance– Assumes DCP and DRGS at 5 degrees elevation

• Availability of power control would provide an additional significant margin of safety

Recommended EIRP Ranges

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Reason for this Choice• Basic Criterion: Under worst case conditions, the

first v.2.0 DCP on GOES 13 must provide acceptable performance into a DRGS with a G/T of 15 dB

• “Worst case” is maximum GOES 11/12 loading, i.e. 112 channels at average EIRP of 48.7 dBmi, all the meeting v.1.0B EIRP requirements

• Proposed minimum EIRPs give Eb/No of 11.7 dB for these conditions

• I do not expect the worst case to actually occur but cannot quantify the improvement

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Assumed Transition Progression

• The proposed large reduction in EIRP is only viable if the transition is coordinated with the change to GOES N/O– GOES N/O has 14 dB more downlink EIRP

• Transition assumes “worst case” loading on GOES 11/12 to “worst case” on GOES 13– GOES 11/12: 112 channels at 48.7 dBmi– GOES-13: 214 channels at 40.3 dBi

• Channels are changed from v.1.0B to v.2.0 and new channels are added at a fixed ratio

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Transition Rule• Additional channels must not be added faster

than old channels can be converted– E.g. change 10% of old channels to new CS (equals

11 channels)– Can then operate 10% of 210 (21 channels) at the CS

v.2.0 EIRP levels• Channels that were not used on GOES 11 or 12

(e.g. channels 1 and 100) can be counted as part of the “changed” channels

• Rule can be applied to whole channels or to specific time periods if the allocation process can handle the complexity

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Minimum EIRPs on GOES 13

• Assumes “worst case” average uplink EIRP• Includes 1 dB margin

 

Minimum Uplink EIRP (dBmi) with Worst Case Transponder Loading, into 15 dB/K DRGS, at Stated Transition Stage

Transition Stage 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

For 300 bps DCPs 38.0 37.8 37.5 37.3 37.1 36.8 36.5 36.2 35.9 35.5 35.2

For 1200 bps DCPs 44.0 43.8 43.5 43.3 43.1 42.8 42.5 42.2 41.9 41.5 41.2

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Transition Options

• Early transitions to CS v.2.0 DCPs could reduce average EIRP on GOES 11/12 and decrease number of low EIRP transmitters

• Some CS v.1.0B DCPs could meet many v.2.0 requirements– EIRPs per v.1.0B are too high to count as v.2.0 – Timing, stability, ACI, etc. could make them “good

neighbors” and remain in use for years– NOAA can monitor actual EIRPs relative to the pilot

level and identify every DCP by address

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Early Change to v.2.0• Any DCP can be changed to a v.2.0 unit at any

time after Wallops receivers are upgraded to comply with v.2.0 (DRGS upgrade?)– The extra channels must not be used until the new

satellite is activated but the DCP can be fully v.2.0 compliant with EIRP the only potential problem

• All EIRPs mentioned herein will work OK into Wallops under all defined conditions

• However, EIRP needed to operate to DRGS with GOES 11 or 12 depends on actual loading

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GOES 11 and 12 Loading

• August 2006 measurements show:– Average is 25 to 30 channels at 45 dBmi – Worst case is 61 channels (2 x 1 second per day)

• March 2007 transponder AGC confirms– Average RF equal to 30 channels at 45 dBmi – Peaks at 55 channels at 45 dBmi (for 4 sec max)

• April 2007 data give same 45 dBmi average– Also show usage of 3.3% to 37% of capacity in the

twelve channels common to both DRGS

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Possible EIRP Options• Create a program to reduce high EIRPs and the

peak number of simultaneous TXs– Set the v.2.0 EIRPs to be compatible

• Allow v.2.0 to set high EIRP ranges for operation with GOES 11 and 12 then require they be lowered for GOES N/P– Remote control of EIRP would be helpful

• Set v.2.0 EIRPs high enough for all satellites and accept higher power requirements

• Require v.2.0 DCPs not be placed in service until after GOES 13 becomes operational

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Possible EIRP Ranges v Loading

Required EIRP ranges for CS v.2.0 (dBmi)

Maximum loading on GOES 11/12 for DRGS

37 to 41 Mid = 3930 channels at 44.5 dBmi avg

80 channels at 40.3 dBmi avg

39 to 43 Mid = 4160 channels at 44.5 dBmi avg

80 channels at 43.2 dBmi avg

41 to 45 Mid = 43105 channels at 44.5 dBmi avg

80 channels at 45.7 dBmi avg

Calculation made for the mid-point of each range1 dB margin is included

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Summary• Proposed EIRPs work into Wallops at all

transition stages at estimated w/c loading• Proposed EIRPs work into 15 dB/K G/T on

GOES-13 at estimated w/c loading• Operation of proposed EIRPs to DRGS on

GOES-11/12 depends on number of simultaneous TXs and average level– Difficult to predict conditions to be used for DRGS

reception conditions– Different ranges could be set for each generation of

satellites

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Recommendations• Recommend 37-41 dBmi for 300 bps and 43-47

dBmi for 1200 bps be accepted for GOES N/P• Recommend additional, higher EIRP levels be

permitted for use with GOES 11 and 12• Propose insert an additional clause in CS v.2.0

subsection 4.1.1– Operation with EIRP up to 47 dBmi for 300 bps links

and 50 dBmi for 1200 bps links is permitted only when transmitting to the GOES 11 or GOES 12 satellites

• Remote control of the EIRP need not be required, but it would make it easer and quicker for users to make adjustments at the transition

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Average Minimum Maximum Total

E on E 44.6 27.9 53.1 160665

W on E 34.8 26.4 51.2 98492

W on W 45.7 29.2 55.5 161186

E on W 35.5 26.9 54.7 90931

All channel EIRP in dBmi measured relative to Pilot

Backup: EIRP Summary Aug 06

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Backup: EIRP on April 8, 2007

• Data from both Signal Engineering and Microcom DRGS reception showed:– Average EIRP on GOES East = 44.7 dBmi– Maximum EIRP on GOES East = 54 dBmi– Only for a subset of GOES East channels but

does tend to indicate stability

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Example: Channel 163

• It seems to be almost fully allocated with 10 second time slots

• 342 allocations with 1 hour repeat intervals• Leaves only 18 slots un-allocated• 342/360 = 95%• However, on April 8, 2007 the actual

transmit time was probably only 32,000 seconds– This is only 37.0% of capacity

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Backup: Channel Usage April 8, 2007

Channel Number

Time Used (%)

Channel Number

Time Used (%)

7 10.9 55 15.2

17 14.2 67 10.8

31 27.7 89 23.3

35 15.3 129 3.3

41 13.9 163 37.0

49 19.2 177 13.7

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Backup: Simultaneous TXs Aug ‘06

Average Number of ST

Maximum Number of ST

East channels on GOES East

18.7 42

All channels on GOES East

27.9 58

West channels on GOES West

15.0 39

All channels on GOES West

26.1 61